Abstract: An aqueous medium for plant tissue culture is provided including a nutritively effective concentration of reduced nitrogen, preferably in the form of an amino acid such as arginine employed in an amount of from 1.0 to 5.0 mM, and having not more that 1.5 mM NH.sub.4.sup.+. A phosphorus compound at a concentration of at least 2.5 mM measured as phosphate is also included. A chelating agent such as EDTA, and an iron compound present in molar excess over the concentration of the chelating agent are employed to control divalent ion concentrations. Potassium ions are maintained at a concentration of below 14 mM. The use of media containing ammonium ions at less than 1.5 mM combined with a supply of reduced nitrogen in the form of arginine, with low potassium levels, has proved useful as media for organized growth, particularly for use with coniferous plants.